An early architectural rendering of the proposed River Walk hotel from March 1966. Construction would begin more than a year later.

An early architectural rendering of the proposed River Walk hotel from March 1966. Construction would begin more than a year later.

Photo: San Antonio Express-News File Photo

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Workers build the foundation of the Hilton Palacio del Rio Hotel on Aug. 26, 1967. Since the hotel was built next to the San Antonio River, it couldn't have a basement. Instead, foundation piers three feet in diameter and 40 feet deep were drilled and a retaining wall was built to anchor the hotel.

Workers build the foundation of the Hilton Palacio del Rio Hotel on Aug. 26, 1967. Since the hotel was built next to the San Antonio River, it couldn't have a basement. Instead, foundation piers three feet in

H.B. Zachry and Barron Hilton oversee construction at the Hilton Palacio del Rio Hotel in August 1967. The hotel was entirely constructed without a permit, and Zachry filed for one after it was finished.

H.B. Zachry and Barron Hilton oversee construction at the Hilton Palacio del Rio Hotel in August 1967. The hotel was entirely constructed without a permit, and Zachry filed for one after it was finished.

Photo: San Antonio Express-News File Photo

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The stretch of the San Antonio River behind the Hilton Palacio del Rio Hotel is seen during the hotel's construction in 1967.

The stretch of the San Antonio River behind the Hilton Palacio del Rio Hotel is seen during the hotel's construction in 1967.

Photo: San Antonio Express-News File Photo

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Construction begins on the shaft of the Hilton Palacio del Rio Hotel on Sept. 12, 1967. The shaft, which was built at an average of more than a foot per hour, houses seven guest and service elevators. Three work shifts with as many as 400 men worked around the clock to complete the shaft in time to add the guest rooms in November.

Construction begins on the shaft of the Hilton Palacio del Rio Hotel on Sept. 12, 1967. The shaft, which was built at an average of more than a foot per hour, houses seven guest and service elevators. Three

Construction continues on the Hilton Palacio del Rio Hotel in the photo from Fall 1967. The hotel was built in three sections, a center section (seen here), and North and South sections made up of prefab guest rooms.

Construction continues on the Hilton Palacio del Rio Hotel in the photo from Fall 1967. The hotel was built in three sections, a center section (seen here), and North and South sections made up of prefab guest

A portion of H.B. Zachry's 300-ton super crane that will lift 35-ton prefab rooms to top of the Hilton Palacio del Rio Hotel is seen on Oct. 25, 1967. The crane cost almost $250,000.

A portion of H.B. Zachry's 300-ton super crane that will lift 35-ton prefab rooms to top of the Hilton Palacio del Rio Hotel is seen on Oct. 25, 1967. The crane cost almost $250,000.

Photo: San Antonio Express-News File Photo

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Crews lift a prefabricated room to stack it onto the Hilton Palacio del Rio Hotel in 1967. Each room weighed 35 tons and was completely decorated — furniture, televisions, towels, everything down to the light bulbs in the lamps — before being lifted into place. The numbered rooms were constructed at a site seven miles from the hotel, and then trucked to the hotel, where they were lifted in order into place using a "whirly bird lifting rig" (the round fan-like part on top of the room) designed by H.B. Zachry to help guide the room into place, much like a tail rotor on a helicopter.

The monolithic modular construction process continues as rooms are added at the Hilton Palacio del Rio Hotel on Nov. 21, 1967. The first room, Room No. 522, was added to the hotel on Nov. 3 on national television, after it was christened by builder H.B. Zachry's wife, Molly. The Zachrys then rode the room into place.

The monolithic modular construction process continues as rooms are added at the Hilton Palacio del Rio Hotel on Nov. 21, 1967. The first room, Room No. 522, was added to the hotel on Nov. 3 on national

A Christmas tree is lifted to the top of the Hilton Palacio del Rio Hotel while HemisFair '68 construction is seen in the background in 1967.

A Christmas tree is lifted to the top of the Hilton Palacio del Rio Hotel while HemisFair '68 construction is seen in the background in 1967.

Photo: San Antonio Express-News File Photo

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The Hilton Palacio del Rio Hotel nears completion on Feb. 27, 1968. It would open a month later on March 30, just seven days before the opening of HemisFair '68.

The Hilton Palacio del Rio Hotel nears completion on Feb. 27, 1968. It would open a month later on March 30, just seven days before the opening of HemisFair '68.

Photo: San Antonio Express-News File Photo

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The completed Hilton Palacio del Rio Hotel is seen in this undated photo. Just 202 days after construction began on the 496-room hotel, it was completed on March 30, just in time for the opening on HemisFair '68 on April 6.

The completed Hilton Palacio del Rio Hotel is seen in this undated photo. Just 202 days after construction began on the 496-room hotel, it was completed on March 30, just in time for the opening on HemisFair

A room at the Hilton Palacio del Rio Hotel is shown after the hotel was completed in 1968. The hotel rooms were done in five different decor schemes, and each room had a color television and AM/FM radio. Now, the rooms feature 37-inch HD TVs and high-speed internet.

A room at the Hilton Palacio del Rio Hotel is shown after the hotel was completed in 1968. The hotel rooms were done in five different decor schemes, and each room had a color television and AM/FM radio. Now,

A four-lane covered carport was added to the Hilton Palacio del Rio Hotel in 1983.

A four-lane covered carport was added to the Hilton Palacio del Rio Hotel in 1983.

Photo: San Antonio Express-News File Photo

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The Fairmount Hotel and the Hilton Palacio del Rio Hotel were briefly neighbors during the Fairmount's big move in the spring of 1985.

The Fairmount Hotel and the Hilton Palacio del Rio Hotel were briefly neighbors during the Fairmount's big move in the spring of 1985.

Photo: San Antonio Express-News File Photo

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The Hilton Palacio del Rio Hotel's geometric facade along San Antonio's River Walk is a visual reminder of how HemisFair '68 changed the Alamo City. The 21-story hotel at 200 S. Alamo St. was built using a modular construction method, opening just in time for the fair. Here's a look at the hotel's construction, which happened in just seven months.

The Hilton Palacio del Rio Hotel's geometric facade along San Antonio's River Walk is a visual reminder of how HemisFair '68 changed the Alamo City. The 21-story hotel at 200 S. Alamo St. was built using a

The Hilton Palacio del Rio Hotel is seen in 1988. The Mariott Hotel is in the backgournd.

The Hilton Palacio del Rio Hotel is seen in 1988. The Mariott Hotel is in the backgournd.

Photo: San Antonio Express-News File Photo

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Guest rooms were modernized and updated as part of a massive $24 million renovation to the Hilton Palacio del Rio Hotel in 2011. The hotel, which had 496 rooms when it was built, now has 485.

Guest rooms were modernized and updated as part of a massive $24 million renovation to the Hilton Palacio del Rio Hotel in 2011. The hotel, which had 496 rooms when it was built, now has 485.

Photo: Robin Jerstad / For The San Antonio Express-News

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Bathrooms were modernized and updated as part of a massive $24 million renovation to the Hilton Palacio del Rio Hotel in 2011.

Bathrooms were modernized and updated as part of a massive $24 million renovation to the Hilton Palacio del Rio Hotel in 2011.

Photo: Robin Jerstad / For The San Antonio Express-News

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In 1968, San Antonio was the home of the Worlds' Fair, HemisFair '68. From April 6 to Oct. 6, a span of seven months, about six million visitors descended on the Alamo City to visit HemisFair, taking in exhibits from more than 30 countries. Click through to learn more about this event, which helped shape San Antonio as we know it today.

PHOTO: The HemisFair '68 campus is seen in March 1968, just days before the fair opened on April 6. Some buildings, including the Tower of the Americas, were still under construction.

In 1968, San Antonio was the home of the Worlds' Fair, HemisFair '68. From April 6 to Oct. 6, a span of seven months, about six million visitors descended on the Alamo City to visit HemisFair, taking in ... more

Photo: San Antonio Express-News File Photo / Photo Illustration

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Nellie Connally, wife of Gov. John Connally, welcomes First Lady Lady Bird Johnson to San Antonio on April 5, 1968, to officially open HemisFair.

Nellie Connally, wife of Gov. John Connally, welcomes First Lady Lady Bird Johnson to San Antonio on April 5, 1968, to officially open HemisFair.

Photo: San Antonio Express-News File Photo

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Among the shaded avenues in the northwest section of HemisFair are the majority of the foreign restaurants. Photo taken in August 1968.

Among the shaded avenues in the northwest section of HemisFair are the majority of the foreign restaurants. Photo taken in August 1968.

Photo: San Antonio Express File Photo

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Visitors crowd the gates on Opening Day of HemisFair '68 on April 6.

Visitors crowd the gates on Opening Day of HemisFair '68 on April 6.

Photo: San Antonio Express-News File Photo

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Visitors walk the grounds on the Opening Day of HemisFair '68 on April 6.

Visitors walk the grounds on the Opening Day of HemisFair '68 on April 6.

Photo: San Antonio Express-News File Photo

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With the Tower of the Americas and the U.S. Confluence Theater in the background, Vice President Hubert H. Humphrey speaks to a large crowd at the U.S. Pavilion Square on Aug. 10, 1968.

With the Tower of the Americas and the U.S. Confluence Theater in the background, Vice President Hubert H. Humphrey speaks to a large crowd at the U.S. Pavilion Square on Aug. 10, 1968.

Photo: San Antonio Express File Photo

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Stephen Sykes of Odessa presses his nose to the glass while taking in the view from the observation deck at the top of the Tower of the Americas during HemisFair '68 on April 11, 1968.

Stephen Sykes of Odessa presses his nose to the glass while taking in the view from the observation deck at the top of the Tower of the Americas during HemisFair '68 on April 11, 1968.

Photo: San Antonio Express-News File Photo

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A champagne toast marks the opening of the restaurant at the top of the Tower of the Americas during HemisFair '68 in April.

A champagne toast marks the opening of the restaurant at the top of the Tower of the Americas during HemisFair '68 in April.

Photo: San Antonio Express-News File Photo

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Abundance of benches at HemisFair provides a cooling rest stop while fairgoers map out their next moves in August 1968. In many cases, they're looking for the shortest route from air conditioned pavilion to air conditioned pavilion. less

Abundance of benches at HemisFair provides a cooling rest stop while fairgoers map out their next moves in August 1968. In many cases, they're looking for the shortest route from air conditioned pavilion to air ... more

Photo: San Antonio Express File Photo

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Diners enjoy the restaurant at the top of the Tower of the Americas on April 15, 1968 during HemisFair '68. The revolving restaurant completes a revolution every hour.

Diners enjoy the restaurant at the top of the Tower of the Americas on April 15, 1968 during HemisFair '68. The revolving restaurant completes a revolution every hour.

Photo: San Antonio Express-News File Photo

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A power failure at the Tower of the Americas stranded an elevator full of tower visitors for 37 minutes on April 25, 1968, during HemisFair '68.

A power failure at the Tower of the Americas stranded an elevator full of tower visitors for 37 minutes on April 25, 1968, during HemisFair '68.

Photo: San Antonio Express-News File Photo

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When the sun gets high overhead, fairgoers search out some of the many shaded areas at HemisFair for a rest break in August 1968. After a few minutes respite, they're up and after more entertainment.

When the sun gets high overhead, fairgoers search out some of the many shaded areas at HemisFair for a rest break in August 1968. After a few minutes respite, they're up and after more entertainment.

Photo: San Antonio Express File Photo

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Gale Dowlearn, 19, a press center employee at HemisFair '68, sits in view of the Tower of the Americas on May 9, 1968.

Gale Dowlearn, 19, a press center employee at HemisFair '68, sits in view of the Tower of the Americas on May 9, 1968.

Photo: San Antonio Express-News File Photo

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HemisFair '68's mini-monorail consisted of ten 40-passenger trains, each with 10 cars, that ferried 4,000 to 4,500 persons per hour across the fair on the 1½-mile long track at a speed of 15 mph.

HemisFair '68's mini-monorail consisted of ten 40-passenger trains, each with 10 cars, that ferried 4,000 to 4,500 persons per hour across the fair on the 1½-mile long track at a speed of 15 mph.

Photo: San Antonio Express-News File Photo

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Original caption: "The Flying Indians of Papantla at HemisFair perform their ancient rain-making ritual by spinning down from the towering pole, but old sol shining brightly in the background left some doubt about impending moisture as this photo was made." Photo taken in August 1968. This popular show featured four Totonac Indians tied by 104-foot ropes around their waists that unwind slowly making 32 revolutions around a 114-foot pole before eventually reaching the ground. However, it began with a bloody chicken sacrifice and one of the maidens was topless. An Express-News story about the Fair's 25th anniversary quoted John Daniels, the fair's attorney, as saying "They had a real live bare-breasted woman up there, and they pretended to sacrifice her as part of the show, but we had a lot of complaints, so they had to cover her up."

Original caption: "The Flying Indians of Papantla at HemisFair perform their ancient rain-making ritual by spinning down from the towering pole, but old sol shining brightly in the background left some doubt

HemisFair guides and hostesses man their electric carts before the start of the Confluence Carts Rally on the HemisFair grounds on Aug. 6, 1968.

HemisFair guides and hostesses man their electric carts before the start of the Confluence Carts Rally on the HemisFair grounds on Aug. 6, 1968.

Photo: San Antonio Express File Photo

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Visitors walk down the stairs at the Tower of the Americas after a power failure on May 22, 1968, during HemisFair '68.

Visitors walk down the stairs at the Tower of the Americas after a power failure on May 22, 1968, during HemisFair '68.

Photo: San Antonio Express-News File Photo

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Kaye Nader and Brenda Herbert soak their feet in a fountain after walking down the tower stairs after a power failure on May 22, 1968.

Kaye Nader and Brenda Herbert soak their feet in a fountain after walking down the tower stairs after a power failure on May 22, 1968.

Photo: San Antonio Express-News File Photo

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Mr. and Mrs. Jimmy Zintgraff were trapped in the Tower of the Americas during a power failure on May 22, 1968, during HemisFair '68.

Mr. and Mrs. Jimmy Zintgraff were trapped in the Tower of the Americas during a power failure on May 22, 1968, during HemisFair '68.

Photo: San Antonio Express-News File Photo

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The full moon seems to be almost resting atop the Tower of the Americas at HemisFair as visitors have their dinner in the tower's restaurant in August 1968. The streak of light on the tower shaft is the elevator taking others up. less

The full moon seems to be almost resting atop the Tower of the Americas at HemisFair as visitors have their dinner in the tower's restaurant in August 1968. The streak of light on the tower shaft is the ... more

Photo: San Antonio Express File Photo

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Visitors to the Texas State Pavilion watch the water fountains during HemisFair '68. The pavilion is now the Institute of Texan Cultures.

Visitors to the Texas State Pavilion watch the water fountains during HemisFair '68. The pavilion is now the Institute of Texan Cultures.

Photo: San Antonio Express-News File Photo

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Fans seek autographs from Bob Hope at HemisFair '68 in May 1968. Other famous visitors to HemisFair included Louis Armstrong and Princess Grace of Monaco.

Fans seek autographs from Bob Hope at HemisFair '68 in May 1968. Other famous visitors to HemisFair included Louis Armstrong and Princess Grace of Monaco.

Photo: San Antonio Express-News File Photo

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Sometimes HemisFair is just too much for kids. When they get tuckered out you'll find them snoozing in the most interesting places. Here, one little girl wraps herself around her dad's neck and catches a few winks. Photo taken in August 1968. less

Sometimes HemisFair is just too much for kids. When they get tuckered out you'll find them snoozing in the most interesting places. Here, one little girl wraps herself around her dad's neck and catches a few ... more

Photo: San Antonio Evening News File Photo

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A family enjoys a meal and the view at the restaurant at the top of the Tower of the Americas on June 14, 1968, during HemisFair '68.

A family enjoys a meal and the view at the restaurant at the top of the Tower of the Americas on June 14, 1968, during HemisFair '68.

Mrs. Winfield S. Hamlin (left), president of the Women's Pavilion at HemisFair, and fair official Bill Sinkin are with directors of various women's components of the Armed Forces (from left): Capt. Veronica ... more

Photo: San Antonio Light File Photo

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A water-skiing clown holds a watermelon during a show on the lagoon at HemisFair '68.

A water-skiing clown holds a watermelon during a show on the lagoon at HemisFair '68.

Photo: San Antonio Express-News File Photo

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The Tower of the Americas appears to be heralded by the Angel Moroni sculpture, part of the Mormon Pavilion, during HemisFair '68 festivities.

The Tower of the Americas appears to be heralded by the Angel Moroni sculpture, part of the Mormon Pavilion, during HemisFair '68 festivities.

Visitors to HemisFair '68 ride the mini-monorail (top) and El Trenecito (the little train, bottom) on July 19, 1968. A round-trip on the monorail cost $1, whereas a trip on the train cost 50 cents for adults and 25 cents for children.

Visitors to HemisFair '68 ride the mini-monorail (top) and El Trenecito (the little train, bottom) on July 19, 1968. A round-trip on the monorail cost $1, whereas a trip on the train cost 50 cents for adults

This is the decorated front fence of the Children's Garden at Project Y at HemisFair in July 1968. The faces were made by elementary school children.

This is the decorated front fence of the Children's Garden at Project Y at HemisFair in July 1968. The faces were made by elementary school children.

Photo: San Antonio Light File Photo

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A family pauses at HemisFair '68 on Aug. 10, 1968.

A family pauses at HemisFair '68 on Aug. 10, 1968.

Photo: San Antonio Express-News File Photo

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Water skier performs on HemisFair Lake as part the Mercury Water Ski Show at HemisFair '68.

Water skier performs on HemisFair Lake as part the Mercury Water Ski Show at HemisFair '68.

Photo: San Antonio Express-News File Photo

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The Queen's own Cameron Regiment Bagpipers, escorting dignitaries to the head table at the Grand Tartan Ball on Aug. 23, 1968, are shown preceding U.S. Pavilion Commissioner and Mrs. Ed Clark as they arrive at the Convention Center. less

The Queen's own Cameron Regiment Bagpipers, escorting dignitaries to the head table at the Grand Tartan Ball on Aug. 23, 1968, are shown preceding U.S. Pavilion Commissioner and Mrs. Ed Clark as they arrive at ... more

Photo: San Antonio Light File Photo

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"The Fair is a Moving Thing" is the title of this undated photo from HemisFair '68, taken by retired Maj. Gen. Joe Lawrie.

"The Fair is a Moving Thing" is the title of this undated photo from HemisFair '68, taken by retired Maj. Gen. Joe Lawrie.

Photo: Courtesy Photo

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Thousands pack the park on the next-to-last day of HemisFair '68 on Oct. 5, 1968.

Thousands pack the park on the next-to-last day of HemisFair '68 on Oct. 5, 1968.

Photo: San Antonio Express-News File Photo

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A statue of St. Anthony graces the exterior of the Portugal Pavilion in the International Sector at HemisFair in August 1968. More than 30 countries participated in the fair, with Japan, Mexico, Italy, Spain, France and Canada hosting large pavilions. less

A statue of St. Anthony graces the exterior of the Portugal Pavilion in the International Sector at HemisFair in August 1968. More than 30 countries participated in the fair, with Japan, Mexico, Italy, Spain, ... more

Photo: San Antonio Light File Photo

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The United States and Texas flags fly at half mast at the Institute of Texan Cultures at the HemisFair '68, in memory of Dr. Martin Luther King, Jr., April 5, 1968, in San Antonio. The Tower of the Americas is in the background. less

The United States and Texas flags fly at half mast at the Institute of Texan Cultures at the HemisFair '68, in memory of Dr. Martin Luther King, Jr., April 5, 1968, in San Antonio. The Tower of the Americas is ... more

Photo: FERD KAUFMAN, Associated Press

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Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Photo: Ralph Crane, Time & Life Pictures / Getty Images

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Country singer Glen Campbell rehearses at HemisFair theater for his show at HemisFair in August 1968.

Country singer Glen Campbell rehearses at HemisFair theater for his show at HemisFair in August 1968.

Photo: Ralph Crane, Time & Life Pictures / Getty Images

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Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Photo: Ralph Crane, Time & Life Pictures / Getty Images

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Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Singer Glen Campbell performs at HemisFair theater during HemisFair in August 1968.

Photo: Ralph Crane, Time & Life Pictures / Getty Images

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Student Shari McGar sells paper flowers at HemisFair in 1968.

Student Shari McGar sells paper flowers at HemisFair in 1968.

Photo: Yale Joel, Time & Life Pictures / Getty Images

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Monorail hostesses dance to the HemisFair Band during HemisFair in 1968.

Monorail hostesses dance to the HemisFair Band during HemisFair in 1968.